Labile compounds and compositions, such as polyunsaturated fatty acids (PUFAs), vitamins, minerals, antioxidants, hormones, amino acids, proteins, carbohydrates, coenzymes, and flavor agents, sensitive to any number of factors, can lose biological or other desired activity when unprotected. In addition, products (for example, decomposition products, degradation products, and oxidation products) that result from the chemical, physical, or biological change or breakdown of labile compounds and compositions, could lack the desired biological function and/or possess unwanted characteristics, such as having off-flavors, undesirable odors, irritation promoting activity and the like. There is often a need to introduce labile compounds and compositions, which are susceptible to chemical, physical, or biological change or breakdown, into pharmaceutical, nutritional, including nutraceutical, and industrial products. In such instances, protection of such compounds and compositions is desirable. With regard to PUFAs in particular, it is desirable to protect such lipids in food products from oxygen, trace metals and other substances which attack the double bonds of the PUFAs. Such protection reduces the likelihood of organoleptic problems, i.e., problems, relating to the senses (taste, color, odor, feel), such as off-flavors and undesirable odors, and other problems, such as loss of physiological activity, for instance. Such protection could potentially increase the shelf life of products containing them.
Encapsulating unstable compounds can protect them from undesirable chemical, physical, or biological change or breakdown while retaining their efficacy, such as biological or physiological efficacy. Microcapsules can exist in powdered form and comprise roughly spherical particles that contain an encapsulated (entrapped) substance. The particle usually has some type of shell, often a polymeric shell, such as a polypeptide or polysaccharide shell, and the encapsulated active product is located within the shell. Microencapsulation of a liquid, such as an oil, allows the formation of a particle that presents a dry outer surface with an entrained oil. Often the particles are a free-flowing powder. Microencapsulation therefore effectively enables the conversion of liquids to powders. Numerous techniques for microencapsulation are known depending on the nature of the encapsulated substance and on the type of shell material used. Methods typically involve solidifying emulsified liquid droplets by changing temperature, evaporating solvent, or adding chemical cross-linking agents. Such methods include, for example, spray drying, interfacial polymerization, hot melt encapsulation, phase separation encapsulation (solvent removal and solvent evaporation), spontaneous emulsion, solvent evaporation microencapsulation, solvent removal microencapsulation, coacervation, and low temperature microsphere formation and phase inversion nanoencapsulation (PIN). Microencapsulation is suitable for drugs, vitamins and food supplements since this process is adaptable by varying the encapsulation ingredients and conditions.
There is a particular need to provide microencapsulated forms of fats or oils, such as vegetable and marine oils, which contain PUFAs. Such microencapsulated forms would benefit from the properties of digestibility, stability, resistance to chemical, physical, or biological change or breakdown. Microencapsulated oils could conveniently be provided as a free flowing powdered form. Such a powder can be readily mixed with other dry or liquid components to form a useful product.
The ability to microencapsulate, however, can be limited by factors due to the nature of the microencapsulation process or the compound or composition to be encapsulated. Such factors could include pH, temperature, uniformity, viscosity, hydrophobicity, molecular weight, and the like. Additionally, a given microencapsulation process may have inherent limitations. For example, in microencapsulation techniques in which heat is used for drying, low-boiling point aromatics can be lost during the drying process. Additionally, the core may adhere to the surface of the encapsulation material, presenting a potential for increased oxidation and changes in the flavor balance of the finished product. In some cases, storage conditions must be carefully controlled to avoid an increase in the water activity and therefore the stability of the capsule and retention of volatiles within the capsule. During spray drying microencapsulation, the feed inlet temperature may not be high enough and result in incomplete drying and sticking in the drying chamber or clump formation in storage. Particulate inconsistencies may also occur under some process conditions. At temperatures that are too low, the particles may balloon and cracks can form in the surface of the particles. This may cause loss of volatile compounds and compromise the quality of the final product. Yet another drawback is that the coatings produced are often water-soluble and temperature sensitive. The present inventors have recognized the foregoing problems and that there is a need, therefore, to provide additional processes for encapsulation of compounds and compositions susceptible to chemical, physical, or biological change or breakdown.